1. Field of the Disclosure
The present invention relates to a method and apparatus for applying a negative pressure. In particular, but not exclusively, the present invention relates to the application of a negative pressure to a wound site in the application of topical negative pressure at the wound site.
2. Background
There is much prior art available relating to the provision of apparatus and methods of use thereof for the application of topical negative pressure (TNP) therapy to wounds together with other therapeutic processes intended to enhance the effects of the TNP therapy. Examples of such prior art include those listed and briefly described below.
TNP therapy (sometimes referred to as Vacuum Assisted Closure or negative pressure wound therapy) assists in the closure and healing of wounds by reducing tissue oedema; encouraging blood flow and granulation of tissue; removing excess exudates and may reduce bacterial load and thus, infection to the wound. Furthermore, TNP therapy permits less outside disturbance of the wound and promotes more rapid healing.
In International patent application, WO 2004/037334, which is incorporated herein by reference, apparatus, a wound dressing and a method for aspirating, irrigating and cleansing wounds are described. In very general terms, the application describes the treatment of a wound by the application of TNP therapy for aspirating the wound together with the further provision of additional fluid for irrigating and/or cleansing the wound, which fluid, comprising both wound exudates and irrigation fluid, is then drawn off by the aspiration means and circulated through means for separating the beneficial materials therein from deleterious materials. The materials which are beneficial to wound healing are recirculated through the wound dressing and those materials deleterious to wound healing are discarded to a waste collection bag or vessel.
In International patent application, WO 2005/04670, which is incorporated herein by reference, apparatus, a wound dressing and a method for cleansing a wound using aspiration, irrigation and cleansing are described. Again, in very general terms, the invention described in this document utilises similar apparatus to that in WO 2004/037334 with regard to the aspiration, irrigation and cleansing of the wound, however, it further includes the important additional step of providing heating means to control the temperature of that beneficial material being returned to the wound site/dressing so that it is at an optimum temperature, for example, to have the most efficacious therapeutic effect on the wound.
However, the above described apparatus and methods are generally only applicable to a patient when hospitalised as the apparatus used is complex, needing people having specialist knowledge in how to operate and maintain the apparatus, and also relatively heavy and bulky, not being adapted for easy mobility outside of a hospital environment by a patient, for example.
Some patients having relatively less severe wounds which do not require continuous hospitalisation, for example, but whom nevertheless would benefit from the prolonged application of TNP therapy, could be treated at home or at work subject to the availability of an easily portable and maintainable TNP therapy apparatus. To this end GB-A-2 307 180 describes a portable TNP therapy unit which may be carried by a patient and clipped to belt or harness. A negative pressure can thus be applied at a wound site.
However, this portable apparatus is still relatively bulky, and may require monitoring of the patient by a trained caregiver. Furthermore, such portable therapy units commonly have reduced capacity to deal with fluid flow rates into a wound cavity caused by leaks. This leads to a greater number of alarms being raised due to an inability to maintain the desired negative pressure at the wound site in the presence of leaks.
Another problem associated with portable apparatus is that on occasion an onboard power source such as a battery pack is used rather than a continuous connection to a power source such as a mains power source. It will be appreciated that such a battery pack has only a limited power resource and therefore TNP therapy can on occasion be halted prior to a desired moment in time because of power failure.
Another problem associated with therapy units which can be utilised by a patient alone without the need for skilled technical assistants is that from time to time warning lights or warning alarms may be initiated when a desired therapy can not be maintained or initiated. This can be distressing for a patient who may not understand the meaning of the cues.
A still further problem associated with the apparatus used to provide TNP therapy is that from time to time a motor associated with a pump which generates a negative pressure will start up or stop. The change in volume coming from the therapy unit can be a cause of concern to a patient.